"Electrum uero quæ apposita sunt, nequaquàm trahit, quem admodum nec lapis ille, qui sideritis nuncupatur, nec quicquā à seipso ad ea quæ in propinquo sunt, extrinsecus assilit. Verum lapis magnes effluxiones quasdam tum graves, tum etiam spiritales emittit, quibus aer continuatus & iunctus repellitur. Is deinceps alium sibi proximum impellit, qui in orbem circum actus, atque ad inanem locum rediens, ui ferrum fecum rapit & trahit. At Electrum uim quandam flammæ similem & spiritalem continet, quam quidem
tritu summæ partis, quo aperiuntur meatus, foras eijcit. Nam leuissima corpuscula & aridissima quæ propè sunt, sua tenuitate atque imbecillitate ad seipsum ducit & rapit, cum non sit adeo ualens, nec tantum habeat ponderis & momenti ad expellendam aeris copiam, ut maiora corpora more Magnetis superare possit & uincere."
[138] Page 54, line 16. Page 54, line 18. Gemma Vincentij rupis.—See the [note] to p. [48] supra, where the name Vincentina occurs.
[139] Page 54, line 30. Page 54, line 35. orobi.—The editions of 1628 and 1633 read oribi.
[140] Page 55, line 34. Page 55, line 42. in euacuati.—The editions of 1628 and 1633 read inevacuati.
[141] Page 58, line 21. Page 58, line 25. assurgentem vndam ... declinat ab F.—These words are wanting in the Stettin editions.
[142] Page 59, line 9. Page 59, line 9. fluore.—This word is conjectured to be a misprint for fluxu but it stands in all editions.
[143] Page 59, line 22. Page 59, line 25. Ruunt ad electria.—This appears to be a slip for electrica, which is the reading of the editions of 1628 and 1633.
[144] Page 60, line 7. Page 60, line 9. tanq materiales radij.—The suggestion here of material rays as the modus operandi of electric forces seems to foreshadow the notion of electric lines of force.
[145] Page 60, line 10. Page 60, line 12. Differentia inter magnetica & electrica.—Though Gilbert was the first systematically to explore the differences that exist between the magnetic attraction of iron and the electric attraction of all light substances, the point had not passed unheeded, for we find St. Augustine, in the De Civitate Dei, liber xxi., cap. 6, raising the question why the loadstone which attracts iron should refuse to move straws. The many analogies between electric and magnetic phenomena had led many experimenters to speculate on the possibility of some connexion between electricity and magnetism. See, for example, Tiberius Cavallo, A Treatise on Magnetism, London, 1787, p. 126. Also the three volumes of J. H. van Swinden, Receuil de Mémoires sur l'Analogie de Electricité et du Magnétisme, La Haye, 1784. Aepinus wrote a treatise on the subject, entitled De Similitudine vis electricæ et magneticæ (Petropolis, 1758). This was, of course, long prior to the discovery, by Oersted, in 1820, of the real connexion between magnetism and the electric current.